Machine tool chuck

ABSTRACT

A machine tool chuck comprising a chuck body having a plurality of clamping jaws slidably mounted thereon and connected to a compensating actuator mechanism which includes an annular member connected to the clamping jaws by intermediate lever means whereby axial displacement of the annular member causes radial displacement of the clamping jaws between open and closed positions. The annular member is radially floatably mounted on a collar which is concentric with and nonrotatably secured to the chuck body, the collar being slidable axially relative to the chuck body and being connected to a suitable power source. A combined centering and locking device coacts between the collar and the floatable annular member for permitting the floatable annular member to be automatically coaxially aligned with the collar and suitably locked in said coaxially aligned position for permitting use of the chuck with concentric clamping action. The centering mechanism, in a preferred embodiment, comprises a centering pin slidably mounted on the collar and having a conical portion adapted to be disposed into a conical recess formed in the annular member for automatically centering the annular member.

of the clamping jaws between open and closed positions. The annularmember is radially floatably mounted on a collar which is con the collarand the floatable annular member for permitting the floatable annular dhaving a o a conical recess ally centering the connected to a suitablepower source. A combined cenmechanism, in a preferred embodiment,comprises a Primary Examiner-Andrew R. J uhasz Assistant Examiner-JamesF. Coan Attorney-Woodhams, Blanchard and Flynn ABSTRACT: A machine toolchuck comprising a chuck body having a plurality of clamping jawsslidably mounted thereon and connected to a compensating actuatormechanism which includes an annular member connected to the clampingjaws by intermediate lever means whereby axial displacement of theannular member causes radial displacement centric with and nonrotatablysecured to the chuck body, the

- 219/15 collar being slidable axially relative to the chuck body andbeing tering and locking device coacts between member to beautomatically coaxially aligned with the collar and suitably locked insaid coaxially aligned position for permitting use of the chuck withconcentric clamping action. The centering centering pin slidably mountedon the collar an conical portion adapted to be disposed int formed inthe annular member for automatic annular member.

III/I IIIIIIIIIIIIIIIII/IIIIIIIYIIIII/II/flvIfiVII/III/Il [50] Field of279/ 1 J 279/1 J 279/ l J B23b 31/16 279/1 TE, 1

References C ted UNITED STATES PATENTS 9/1958Lammens.....................

SM m N" Em T Am m N Pierre E. Renoux Colombes, France Apr. 30, 1969 [45]Patented Dec. 28, 1971 Cri-Dan Paris, France July 3, 1968 France MACHINETOOL CHUCK 1 1 Claims, 4 Drawing Figs.

6/1957 Sampson Assignee United States Patent [72] Inventor [21] Appl.No.[22] Filed [32] Priority IIIIIIIIIIJTIIIA'III PAIENTEU M02819?! 30,535

SHEET 2 OF 2 MACHINE TOOL cnucx The present invention relates to amachine tool chunk, especially for machine tools of the lathe type,comprising a chuck body in which is slidably mounted a set of clampingjaws actuated by an eccentricity compensation mechanism consisting of afloating annular member mounted on a collar which is capable of slidinglongitudinally with respect to the chunk body under the action ofcontrol jacks, said annular member being provided with inclined rampsadapted to cooperate with levers for operating the jaws at the time oftranslational motion of the annular member.

IN machine tools of the lathe type, the chunk usually has three jaws andserves to secure the workpiece to the power spindle. Chunks of thecompensation type are already in use for the purpose of driving aworkpiece in rotation, the rotational axis of the workpiece beingdefined by means such as centers which are independent of the clampingjaws.

In another known type of chuck, some of the jaws which may be three innumber, for example, are actuated by a mechanism designed to produce aclamping action which is concentric with the rotational axis of thespindle whilst different jaws which may also be three in number areactuated by another clamping mechanism which provides compensation foreccentricity.

However, in some applications and especially when machining tubes ofsubstantial length which have to be engaged through the spindle of themachine, it can be an advantage to provide the possibility of clampingthe workpiece by means of a chunk in which all the jaws are capable ofproviding either concentric clamping or compensation clamping inaccordance with requirements. Although chunks of this type alreadyexist, they are not as a rule very convenient in practice since theoperation which is necessary in order to change from concentric clampingto compensation clamping or conversely always entails a time intervalduring which the machine tool is immobilized to no useful purpose.Moreover, in order to carry out this operation it is first necessary inthe majority of cases to withdraw the workpiece from the spindle, whichis not always desirable and further increases the outage time of themachine.

The present invention is primarily intended to overcome theabove-mentioned disadvantages and is accordingly directed to a chuck ofthe above-mentioned type which is essentially characterized in that saidchuck further comprises a locking device which can be remotely operatedso that the floating device which can be remotely operated so that thefloating annular member may be recentered and secured at will relativeto the axis of the chuck and the clamping action of the chuck may thusbe made concentric.

It can readily be understood that, by virtue of this arrangement, theoperation which is necessary in order to change over from concentricclamping of the chuck to compensation clamping or conversely can becarried out virtually instantaneously and without any need to remove theworkpiece, from the spindle, for example by depressing a simple electricselection contact. Thus, the operation of the machine tool ispractically not interrupted.

As a preferable feature, the locking device is locked automatically eachtime the jaws open and is unlocked at will by means of the remotecontrol system.

In this manner, the chunk is always in the concentric clamping conditionat the outset and it is necessary to operate a pushbutton selector wheneccentricity compensation clamping is required.

As an advantageous feature, the remote control of the locking device iscarried out by means of some of the jaw-actuating jacks.

By virtue of this arrangement, it is not necessary to employ any sourceof auxiliary power in order to make a selection between concentricclamping and compensation clamping of the chuck, thereby reducing thecost price of the chuck to a considerable extent.

In a particular embodiment of the invention, the locking devicecomprises conical studs which are slidably mounted on the collar of thecompensation mechanism and adapted to cooperate with correspondingconical recesses formed in the floating annular member, stops which aresecured to the chuck body and adapted to cooperate with the studs at oneend thereof in order to thrust said studs into said recesses at the timeof translational motion of the collar which results in opening of thejaws, and a drive unit which can be remotely operated in order to thrustsaid studs away from said recesses when so required.

Preferably, the drive unit is constituted by one or a number ofjaw-actuating jacks, the operating rods of the said jacks being securedto an annular disc so as to insure that the sliding collar is driven intranslational motion by said jacks only in the direction whichcorresponds to clamping of the jaws whilst the operating rods of theother jacks are rigidly coupled to the collar for translational motionin both directions, said annular disc being adapted to cooperate withthe opposite extremities of the studs in order to force said studs awayfrom the recesses at the time of a relative movement of the disc withrespect to the collar and to the floating annular member.

A chuck of this type can easily be produced at low cost and alsoprovides high operational reliability.

Suitably, the stops which serve to carry out automatic recentering ofthe floating annular member each time the jaws open are capable of beingwithdrawn so that the chunk may thus be employed with compensationclamping over long periods without entailing the need to actuate thelocking device every time. Premature wear of said device is thusprevented.

A better understanding of the invention will be obtained from thefollowing description, reference being made to the accompanying drawingsin which one exemplified embodiment is shown by way of nonlimitativeexample, and wherein:

FIG. I is a simplified front view of a machine tool chunk in accordancewith the invention;

FIG. 2 is an axial sectional view taken along line II-II of FIG. 1;

FIG. 3 is a fragmentary sectional view taken along line III- III of FIG.1; and FIG. 4 is a fragmentary sectional view which is similar to FIG. 3and shows the chuck components in a different operating position.

The chuck which is shown in the figures is essentially constituted by acylindrical chunk body 1 in which clamping jaws 2 are mounted to pennitradial sliding motion. In the example of construction herein described,said jaws are six in number and are uniformly spaced at angularintervals of 60.

The chuck body 1 is secured by means of screws 3 to the rotary spindle 4of a machine tool of the lathe type. The stationary or nonrotatingportion of the chuck is secured by means of screws 5 to the headstock 6of said machine tool by means of an annular plate 7 which carries theprotective chuck casing 8. There is also shown at 9 a workpiece in theform of a tube, the end of which is to be machined and which passesentirely through the spindle 4 along the rotational axis of this latter.

The clamping jaws 2 are operated by a compensating actuator mechanism ofknown type whereby opening or closure of said jaws can be carried out atwill while making it possible within certain limits to compensate forgeometrical defects of the clamped surface with respect to the centeredsurface of the part to be machined. This mechanism comprises levers l0pivoted about pins 11 which are carried by the chuck body 1, each leverbeing adapted to actuate one of the jaws 2 by means of an extremity 12in the form of a bearing knuckle which is adapted to cooperate with acorresponding recess formed in the jaw. The other end of each lever 10is fitted with a runner wheel 13 in cooperating relation with inclinedramps 14 which are formed in a floating annular member 15. Said floatingannular member 15 is mounted with a predetermined radial play on asliding collar 16 by virtue of means which are described hereinafter.

Alternately arranged washers l7 and 18 are interposed between theannular member and the collar 16. The washers 17 are centered within theannular member 15 without play while having a certain play with respectto the collar 16 whereas the washers 18 are centered on the collar 16without play but have a certain play with respect to the annular member15. The number of said washers 17 and 18 is determined as a function ofthe desired minimum clamping force of the chuck.

The collar 16 is capable of sliding axially over the chuck body 1 but isdriven in rotation with this latter by means of one or a number of guidekeys 19. The axial displacement of said collar 16 is produced by meansof jacks such as the jack 20 which are preferably of the pressure-fluidtype and mounted on the annular plate 7 which is rigidly fixed to theheadstock 6 of the machine tool. The piston rods 21 of said jacks 20 aresecured to an annular member 22 which is coupled to the collar 16 bymeans of a ball-thrust bearing 23 or any like rotary seal of suitabletype such as a pad-thrust or roller-thrust bearing. It accordinglybecomes apparent that, depending on whether the fluid pressure isapplied on either one face of the pistons of the jacks 20 or on theother, the collar 16 is displaced axially either in one direction or inthe other and therefore causes either the clamping of the jaws 2 againstthe tube 9 with compensation for eccentricity of this latter or thereleasing of said jaws.

In accordance with the invention, the chuck further comprises a lockingdevice whereby the annular member 15 is keyed radially with respect tothe collar 16 whenever this is desired, This locking device isessentially constituted by studs 24 which are six in this example ofconstruction and are slidably mounted on the collar 16. Each stud has aconical portion 25 which is capable of engaging in a correspondingconical recess 26 formed in the annular member 15 so that this lattermay be recentered and locked in position with respect to the collar 16as and when required.

The studs 24 are capable of longitudinal displacement with respect tothe collar 16 between two end positions materialized by a detent ball 27which is subjected to the action of a spring 28. Said ball 27 is appliedeither within a channel 29 of the stud which corresponds to locking ofthe annular member 15 or against the conical portion 25 whichcorresponds to unlocking of said annular member.

The studs 24 are also provided at each end with a pushrod as designatedrespectively by the references 30 and 31. Each pushrod 30 is associatedwith a stop which is rigidly flxed to the chuck body, said stop beingconstituted in this example by a detachable screw 32. The screws 32 arealso accessible from the exterior through recesses 33 which are formedin the front face of the chuck body and which are normally sealed off bymeans of plugs 34.

The pushrods 31 are in turn adapted to cooperate with an annular member35 which is disposed between the annular member 15 and the annularmember 22, said member 55 being capable of axial displacement withrespect to the chuck body 1 under the action ofjacks such as the jack 36so as to come into contact with the ends of said pushrods. The operatingrods 37 of the jacks 36 are secured to the annular member 35 and mountedso as to permit free sliding motion of said rods through suitablerecesses in the annular member 22. Thus, when the jack rods 37 movetowards the left as shown in FIG. 4, only the annular member 35 isactuated whereas, when said operating rods move towards the right, theannular member 22 is also actuated. On the contrary, when the operatingrods 21 of the jacks 20 move towards the left, both annular members 22and 35 are driven at the same time whereas, in the other direction, onlythe member 22 is actuated.

The chuck in accordance with the invention is therefore provided withtwo types of jacks: jacks 20 having operating rods 21 which are securedto the annular member 22, and jacks having operating rods 37 which aresecured to the annular member 35. In the example of construction hereindescribed, there are three jacks of each type, namely a total of six,which are disposed alternately and at uniform angular intervals.

Provision is also made for a microswitch 38 so that the supply of fluidto the jacks can be reversed automatically. Said microswitch is mountedon a stationary portion of the chuck, for example on the body of one ofthe jacks 36 and can be actuated by means of a runner wheel against ahorizontal bearing surface 39 of the annular member 22 which is providedat one end with a chamfered edge 40.

The chuck which has just been described operates as follows:

It will first be noted that, as each opening motion of the jaws 2 takesplace, that is to say when the collar 16 and the annular member 15 carryout a movement of displacement from the position shown in FIG. 2 towardsthe left-hand side under the action of the jacks 20, the pushrods 30 ofthe studs 24 come into contact with the stops 32 at the end of thereleasing action. The studs 24 are consequently displaced towards theright if they were not already in that position and automatically effectrecentering as well as radial locking of the annular member 15 withrespect to the collar 16 by virtue of the conical portion 25 whichcooperates with the corresponding recess 26 of the annular member. Itwill also be noted that this operation can be carried out even when thechuck continues to rotate inasmuch as the studs 24 are rotationallycoupled to the chuck body 1 which carries the stops 32. The annularmember 15 of the chuck is thus always locked to the collar 16 at theoutset and the studs 24 take up the position shown in FIG. 2 or FIG. 3in which the balls 27 are applied within the channels 29.

If the six jacks 20 and 36 are now actuated simultaneously for theclamping operation, that is to say if said jacks are supplied with fluidso that the operating rods 21 and 37 withdraw into the interior of thejack bodies, the entire moving system 22-23-35-24-15-16-17-18 isactuated at the same time. The clamping of the jaws 2 against the tube 9is accordingly concentric since the floating annular member 15 remainslocked to collar 16 of the studs 24.

On the other hand, if the three jacks 20 are actuated solely forclamping action whilst the three jacks 36 remain supplied in the releasecondition, only the moving system 22-23-15- 16-17-18 is actuated and theannular member 35 remains in its initial position. The pushrods 31 aretherefore abuttingly applied against said annular member 35 and displacethe studs 24 towards the left away from the recesses 26 of the annularmember 15 until the balls 27 are applied against the conical portions 25as illustrated in FIG. 4. The floating annular member 15 of the chuck isaccordingly unlocked and has a certain radial play with respect to thecollar 16. It will be noted that this operation is possible only whenthe chuck is stopped, which is practically always the case at the momentof clamping of the workpiece since the annular member 35 is securedagainst rotation with respect to the headstock 6 whereas the studs 24rotate with the chuck body 1.

At the end of a predetermined travel of the annular member 22, thechamfered edge 40 of the bearing surface 39 of the said member comesinto contact with the runner wheel of the microswitch 38, therebycausing the reversal of the fluid supply to the three jacks 36. Theoperating rods 37 of the said jacks accordingly draw back the annularmember 35, then the annular member 22, and finally cooperate with thethree jacks 20 so as to carry out effective clamping of the jaws 2around the periphery of the tube 9.

Since the annular member 15 is unlocked, the clamping action justreferred to is of the eccentricity-compensation type. In other words,the jaws 2 come into position in such a manner as to be adapted to theexternal surface of the tube 9 without applying any force other than aclamping force which is equalized between the different jaws. Thefriction forces generated by the axial thrust of the jacks between thesurfaces of the washers 17 an 18 and the corresponding surfaces of thecollar 16 and of the annular member 15 result in positional locking ofsaid member 15 and in irreverablitly of the compensation motion.

By means of the chuck according to the invention, either a clampingaction which is concentric with the axis of the spindle or a clampingaction which provides compensation for eccentrictiy may accordingly beprovided at will. Changeover from one to the other may be carried outautomatically and practically instantaneously by any suitable means suchas a simple two-position electric pushbutton selector which controls theoperation of the jacks and 36. Said selector can also consist of a relaywhich is incorporated in the sequence of an automatic machine.

The stops 32 can naturally be unscrewed by hand after removal of theplugs 34. Under these conditions the annular member 15 remains unlocked,with the result that the chuck accordingly operates continuously witheccentricity-compensation clamping without any need to carry outelectric selection prior to each operation. This has the effect ofpreventing premature wear of the locking device when concentric clampingof the chuck is not required over a long period of service.

lt will also be readily apparent that the embodiment of the invention ashereinabove described has been given solely by way of example withoutany limitation being implied and that any number of modifications mayaccordingly be contemplated without thereby departing from the scope ofthe invention.

What we claim is:

1. In combination, a machine tool chuck having a chuck body and aplurality of clamping jaws slidably mounted on said chuck body forradial movement relative to said chuck body between open and closedpositions a driving member coaxially aligned with and nonrotatablyinterconnected to said chuck body, said driving member being mounted foraxial movement relative to said chuck body, and compensating actuatormeans drivingly connected between said driving member and said clampingjaws for permitting movement of said jaws in response to axial movementof said driving member and for additionally permitting the radialposition of said jaws to compensate for eccentricity of a workpiece,said compensating actuator means including an annular member mounted onsaid driving member for free radial floating movement relative theretoand intermediate link means drivingly connected between said floatingannular member and said clamping jaws, the improvement comprising acentering mechanism coacting with said floating annular member forpermitting said floating annular member to be repositioned in coaxialalignment with and radially secured relative to said chuck body toenable the clamping action of the tool chuck to be made concentricrelative to the chuck body.

2. A chuck accordingly to claim 7, wherein said centering mechanismincludes a centering pin mounted on one of said driving and floatingmembers for sliding movement between first and second positions, saidcentering pin having a conical portion adapted to be disposed within aconical recess formed in the other of said driving and floating memberswhen said centering pin is in said first position for causing saidfloating member to be aligned with said driving member, said centeringpin when in said second position having the conical portion thereofsubstantially withdrawn from said conical recess for permitting freeradial floating movement of said floating member.

3. A chuck according to claim 2, wherein said centering pin is slidablymounted on said driving member and said conical recess if formed in saidfloating member.

4. A chuck according to claim 3, further including springurged detentmeans mounted on said driving member and disposed for coaction with saidcentering pin for releasably resiliently locking said centering pin ineither said first position or said second position.

5. A chuck according to claim 3, wherein said driving member and saidfloating member are axially movable as a unit between first and secondaxially spaced locations for causing said clamping jaws to be movedbetween open and closed positions, respectively, and further includingstop means mounted on said chuck body and disposed for contacting saidcenterin pin for causing said centerin pin to be moved into said irstposition so as to automatica ly recenter said floating member wheneversaid driving member and said floating member are moved toward said firstlocation.

6. A chuck according to claim 3, further including movable release meansdisposed for coaction with said centering pin for permitting movement ofsaid centering pin from said first position to said second position toradially release said floating member from said driving member, saidrelease means including a movable release member disposed for movementin a direction substantially parallel to the axis of said chuck body.

7. A chuck according to claim 6, wherein said driving member and saidfloating member are axially movable as a unit between first and secondaxially spaced locations for causing said clamping jaws to be movedbetween said open and closed positions, respectively, and furtherincluding stop means mounted on said chuck body and disposed forcontacting said centering pin for causing said centering pin to be movedinto said first position so as to automatically recenter said floatingmember whenever said driving member and said floating member are movedtoward said first location.

8. A chuck according to claim 7, wherein a first power unit is connectedto said driving member for causing axial movement thereof between saidfirst and second locations, and wherein said release means includes asecond power unit connected to said release member for causing axialmovement thereof independently of said first power unit.

9. A chuck according to claim 8, wherein said release member is movableby said second power means between a released position spaced from andout of engagement with said centering pin and an engaged positionwherein said release means engages said centering pin and moves same tosaid second position, said release member having a portion thereofdisposed between said centering pin and said driving member andpositioned within the path of movement of said driving member wherebysaid release member is movable relative to said driving member from saidreleased position to said engaged position, movement of said releasemember by said second power means from said engaged position to saidreleased position causing said portion to engage said driving member tocause movement of said driving member toward said first location whereinsaid clamping jaws are in the open position.

10. A chuck according to claim 1, further including means coacting withsaid centering mechanism for automatically actuating said centeringmechanism and causing said floating member to be recentered wheneversaid clamping jaws are moved to the open position.

11. A chuck according to claim 1, further including actuator meansselectively actuatable and disposed for selective coaction with saidcentering mechanism to cause said centering mechanism to be movedbetween a first position wherein said annular member and said chuck bodyare coaxially fixedly secured and a second position wherein said annularmember is radially floatable relative to said chuck body, whereby saidchuck can thus be utilized either concentrically or eccentricallyrelative to the longitudinal axis thereof.

1. In combination, a machine tool chuck having a chuck body and aplurality of clamping jaws slidably mounted on said chuck body forradial movement relative to said chuck body between open and closedpositions, a driving member coaxially aligned with and nonrotatablyinterconnected to said chuck body, said driving member being mounted foraxial movement relative to said chuck body, and compensating actuatormeAns drivingly connected between said driving member and said clampingjaws for permitting movement of said jaws in response to axial movementof said driving member and for additionally permitting the radialposition of said jaws to compensate for eccentricity of a workpiece,said compensating actuator means including an annular member mounted onsaid driving member for free radial floating movement relative theretoand intermediate link means drivingly connected between said floatingannular member and said clamping jaws, the improvement comprising acentering mechanism coacting with said floating annular member forpermitting said floating annular member to be repositioned in coaxialalignment with and radially secured relative to said chuck body toenable the clamping action of the tool chuck to be made concentricrelative to the chuck body.
 2. A chuck accordingly to claim 7, whereinsaid centering mechanism includes a centering pin mounted on one of saiddriving and floating members for sliding movement between first andsecond positions, said centering pin having a conical portion adapted tobe disposed within a conical recess formed in the other of said drivingand floating members when said centering pin is in said first positionfor causing said floating member to be aligned with said driving member,said centering pin when in said second position having the conicalportion thereof substantially withdrawn from said conical recess forpermitting free radial floating movement of said floating member.
 3. Achuck according to claim 2, wherein said centering pin is slidablymounted on said driving member and said conical recess is formed in saidfloating member.
 4. A chuck according to claim 3, further includingspring-urged detent means mounted on said driving member and disposedfor coaction with said centering pin for releasably resiliently lockingsaid centering pin in either said first position or said secondposition.
 5. A chuck according to claim 3, wherein said driving memberand said floating member are axially movable as a unit between first andsecond axially spaced locations for causing said clamping jaws to bemoved between open and closed positions, respectively, and furtherincluding stop means mounted on said chuck body and disposed forcontacting said centering pin for causing said centering pin to be movedinto said first position so as to automatically recenter said floatingmember whenever said driving member and said floating member are movedtoward said first location.
 6. A chuck according to claim 3, furtherincluding movable release means disposed for coaction with saidcentering pin for permitting movement of said centering pin from saidfirst position to said second position to radially release said floatingmember from said driving member, said release means including a movablerelease member disposed for movement in a direction substantiallyparallel to the axis of said chuck body.
 7. A chuck according to claim6, wherein said driving member and said floating member are axiallymovable as a unit between first and second axially spaced locations forcausing said clamping jaws to be moved between said open and closedpositions, respectively, and further including stop means mounted onsaid chuck body and disposed for contacting said centering pin forcausing said centering pin to be moved into said first position so as toautomatically recenter said floating member whenever said driving memberand said floating member are moved toward said first location.
 8. Achuck according to claim 7, wherein a first power unit is connected tosaid driving member for causing axial movement thereof between saidfirst and second locations, and wherein said release means includes asecond power unit connected to said release member for causing axialmovement thereof independently of said first power unit.
 9. A chuckaccording to claim 8, wherein said release member is movable by saidsecond power means between a released position spaced frOm and out ofengagement with said centering pin and an engaged position wherein saidrelease means engages said centering pin and moves same to said secondposition, said release member having a portion thereof disposed betweensaid centering pin and said driving member and positioned within thepath of movement of said driving member whereby said release member ismovable relative to said driving member from said released position tosaid engaged position, movement of said release member by said secondpower means from said engaged position to said released position causingsaid portion to engage said driving member to cause movement of saiddriving member toward said first location wherein said clamping jaws arein the open position.
 10. A chuck according to claim 1, furtherincluding means coacting with said centering mechanism for automaticallyactuating said centering mechanism and causing said floating member tobe recentered whenever said clamping jaws are moved to the openposition.
 11. A chuck according to claim 1, further including actuatormeans selectively actuatable and disposed for selective coaction withsaid centering mechanism to cause said centering mechanism to be movedbetween a first position wherein said annular member and said chuck bodyare coaxially fixedly secured and a second position wherein said annularmember is radially floatable relative to said chuck body, whereby saidchuck can thus be utilized either concentrically or eccentricallyrelative to the longitudinal axis thereof.